[PATCH 2 of 4] revlog: calculate base revisions iteratively

[Sune Foldager]

# HG changeset patch
# User Sune Foldager <cryo at cyanite.org>
# Date 1304611530 -7200
# Node ID e94b057be38fc9362d4ea3f50d22d0470502b617
# Parent  1b9d53b3eb06728afc9aae4198a53fd0e05e04e9
revlog: calculate base revisions iteratively

This is in preparation for generaldelta, where the revlog entry base field
is reinterpreted as the deltaparent. For that reason we also rename the base
function to chainbase.

diff -r 1b9d53b3eb06 -r e94b057be38f mercurial/commands.py
--- a/mercurial/commands.py	Thu May 05 18:05:24 2011 +0200
+++ b/mercurial/commands.py	Thu May 05 18:05:30 2011 +0200
@@ -1565,13 +1565,13 @@
             except:
                 pp = [nullid, nullid]
             ui.write("% 6d % 9d % 7d % 6d % 7d %s %s %s\n" % (
-                    i, r.start(i), r.length(i), r.base(i), r.linkrev(i),
+                    i, r.start(i), r.length(i), r.chainbase(i), r.linkrev(i),
                     short(node), short(pp[0]), short(pp[1])))
         elif format == 1:
             pr = r.parentrevs(i)
             ui.write("% 6d %04x % 8d % 8d % 8d % 6d % 6d % 6d % 6d %s\n" % (
                     i, r.flags(i), r.start(i), r.length(i), r.rawsize(i),
-                    r.base(i), r.linkrev(i), pr[0], pr[1], short(node)))
+                    r.chainbase(i), r.linkrev(i), pr[0], pr[1], short(node)))
 
 def debugindexdot(ui, repo, file_):
     """dump an index DAG as a graphviz dot file"""
diff -r 1b9d53b3eb06 -r e94b057be38f mercurial/revlog.py
--- a/mercurial/revlog.py	Thu May 05 18:05:24 2011 +0200
+++ b/mercurial/revlog.py	Thu May 05 18:05:30 2011 +0200
@@ -319,8 +319,13 @@
         return self.start(rev) + self.length(rev)
     def length(self, rev):
         return self.index[rev][1]
-    def base(self, rev):
-        return self.index[rev][3]
+    def chainbase(self, rev):
+        index = self.index
+        base = index[rev][3]
+        while base != rev:
+            rev = base
+            base = index[rev][3]
+        return base
     def flags(self, rev):
         return self.index[rev][0] & 0xFFFF
     def rawsize(self, rev):
@@ -856,7 +861,6 @@
         # look up what we need to read
         text = None
         rev = self.rev(node)
-        base = self.base(rev)
 
         # check rev flags
         if self.flags(rev) & ~REVIDX_KNOWN_FLAGS:
@@ -865,10 +869,13 @@
 
         # build delta chain
         chain = []
+        index = self.index # for performance
         iterrev = rev
-        while iterrev != base and iterrev != cachedrev:
+        e = index[iterrev]
+        while iterrev != e[3] and iterrev != cachedrev:
             chain.append(iterrev)
             iterrev -= 1
+            e = index[iterrev]
         chain.reverse()
         base = iterrev
 
@@ -990,7 +997,7 @@
                 delta = mdiff.textdiff(ptext, t)
             data = compress(delta)
             l = len(data[1]) + len(data[0])
-            base = self.base(rev)
+            base = self.chainbase(rev)
             dist = l + offset - self.start(base)
             return dist, l, data, base